Abstract: In order to further reduce the loss of maize machinery harvest,this paper conducted different harvest period and machine harvest rate tests in Bayan County,Yi’an county and 852 farm in 2018 and Keshan Branch of Heilongjiang Academy of Agricultural Sciences in 2020.The effects of different factors on the loss of maize machinery harvest were investigated.The results showed that under the normal growth condition,when the moisture content of maize grain was between 23%and 25%,the loss was the lowest,which was the best period of mechanical grain harvest,and the best mechanical harvest speed was about 1.5 m·s^-1;under the normal growth condition,when the moisture content of mazie grain was between 28%and 33%,the loss was the lowest,which was the best period of mechanical ear harvest,and the best mechanical harvest speed was between1.5-2.0 m·s^-1.In the lodging field the method of early harvest period and lower the mechanical harvest speed could reduce the mechanical harvest loss.